Cycloolefins can be polymerized through the olefin structure to yield polycycloaliphatics, or through a ring opening process to yield unsaturated linear polymers. The latter process has particular appeal, since the polymers so made are sulfur-vulcanizable. Since cyclopentene is a readily available ethylene production by-product, much of the art focuses on the ring-opening polymerization and copolymerization of cyclopentene.
U.S. Pat. No. 3,790,545 teaches ring-opening polymerization of cyclopentene at a temperature from about -40.degree. C to about -60.degree. C and lower with a catalyst comprising a tungsten salt, an organoaluminum compound and, optionally, an acyclic olefin molecular weight modifier. The tungsten salt is added after the organoaluminum compound and at polymerization temperatures. The general application of broad prior art teachings such as that of U.S. Pat. No. 3,790,545 to the copolymerization of cyclopentene with dicyclopentadiene results in no reaction occurring, or if a reaction occurs, the polymer produced is substantially insoluble, i.e., greater than 10% insoluble in a solvent defined hereinafter. Substantial insolubility indicates the presence of gel and/or dicyclopentadiene homopolymer. A method is desired of making a copolymer of cyclopentene with dicyclopentadiene that is greater than 90% soluble in a solvent defined hereinafter in order to simplify polymer compounding and polymer removal from polymerization vessels.
U.S. Pat. No. 3,778,420 teaches preparation of copolymers of a cyclic monoolefin and up to 50% by weight of a cyclic polyolefin. A new copolymer is desired having positive green strength.